In recent years the complexity of electrical circuits has reached a point such that the number of input and output pads frequently is too large to be accommodated on the periphery of an electronic chip or interconnect substrate. Furthermore, the number of input and output pads can easily be in excess of what can conveniently be handled by means of prior art cantilever probes.
In order to overcome the limitations of the cantilever probe technique, so-called "buckling beam" probes have been developed. See U.S. Pat. No. 3,806,801, which discloses a high density, constant force probe assembly utilizing buckling wires.
Numerous variations on the basic buckling beam probe are also known to the art. For instance, U.S. Pat. No. 4,506,215 discloses an assembly that uses a centerpost and guide plates to align the beams, with pre-bow induced in the beams. The patent also discloses the presence in the assembly of guidepins that are angled relative to the buckling beams to induce a wiping action of the buckling beams on the test points when a load is applied to buckling beams contacting the circuit test points.
U.S. Pat. No. 4,518,910 discloses a buckling beam assembly that comprises a central post comprising a spring-loaded plunger and a nut and bolt arrangement that permits resurfacing of the contact tips to insure longer life for the buckling beams. Other variations are disclosed, for instance, in U.S. Pat. Nos. 4,622,514 and 4,686,464, with the latter disclosing a buckling beam probe assembly comprising a number of sub-assemblies, each of which has a multiplicity of buckling beams arranged in an area array form. See also, for instance, E. J. Dombroski, et al, IBM Technical Disclosure Bulletin, Vol. 18 (4), pp. 1038-1039; L. H. Faure, op. cit., Vol. 19 (4), pp. 1267-1268; L. D. Lipschutz, et al, op. cit., Vol. 15 (10), pp. 3032-3034; A. Kostenko, op. cit., Vol. 15 (10), page 3035; and A. Kostenko, op. cit., Vol. 15 (11), page 3543.
Although the prior art knows a number of buckling beam probe assemblies there still exists a need for a simple and convenient assembly that can accommodate an area array of probes, that potentially can accommodate hundreds of probes, wherein the probes exert substantially identical contact force on the respective test pads, and which optionally is adapted for probe tip repair and/or for direct optical monitoring of placement of the probe array onto the array of test points, and which optionally can accommodate bare probe wires. This application discloses such an assembly.